Floatable vessel

ABSTRACT

A floatable vessel comprising a single upright buoyant column of relatively small cross-section which carries, at the lower column end, a floatable ballast chamber of relatively large crosssection. The vessel further comprises a buoyant superstructure also of relatively large cross-section slidably mounted on the column and securable thereto. Arranged within the column is a duct which extends over the height of the vessel and is open at the lower end of the vessel. The ballast chamber has a conical base which provides an inverted funnel leading to the duct opening at the lower end of the vessel. By virtue of the slidable mounting of the superstructure on the column, the vessel is either in a towing condition for towing the vessel to the intended site or it is in an operating condition in which the ballast chamber and a relatively large proportion of the column are submerged. In this condition, the vessel may be used for recovering oil escaping from the sea bed.

Unlted States Patent 11 1 1111 3,921,558

Redshaw Nov. 25, 1975 FLOATABLE VESSEL [57] ABSTRACT lnvemori LeonardRedshaw, Lancashire, A floatable vessel comprising a single uprightbuoyant England column of relatively small cross-section which carries,[73] Assigneez Vickers Limited, London, England at the lower column end,a floatable ballast chamber of relatively large cross-sect1on. Thevessel further 1 Flled? p 1974 comprises a buoyant superstructure alsoof relatively [21] AppL No: 506,407 large cross-section slidably mountedon the column and securable thereto. Arranged w1th1n the column 15 aduct which extends over the height of the vessel and U-S- Cl. is pen atthe lower end of the vesseL The ballast [51] Int. Cl. B63B 35/44 chamberhas a Conical base which provides an [58] Fleld of Search 114/5 T, D;9/8 P; verted funnel leading to the duct opening at the lower 61/46-5, 11 F end of the vessel. By virtue of the slidable mounting of thesuperstructure on the column, the vessel is either References Cited in atowing condition for towing the vessel to the in- UNITED STATES PATENTStended site or it is in an operating condition in which 3,165,898 1/1965Elliott 114/.5 D x the ballast Chamber and a relatively large Proportion3,408,821 11/1968 Redshaw 114 .5 D X of h column r g I this condition,the 3,470,838 10/1969 Daniell 114/.5 D vessel may be used for recoveringoil escaping from 3,664,136 5/1972 Laval et a1. 61/1 F the sea bed.3,667,605 6/1972 Zielinski 61/1 R X 3,738,113 6/1973 Madary et a1.114/.5 T X 3,745,773 7/1973 Cunningham 61/1 F X Primary Examiner-TrygveM. Blix Assistant ExaminerSherman D. Basinger 10 5 Drawmg FguresAttorney, Agent, or Firm-Thomas C. Wettach; Arland T. Stein 8 24 7 H 23LE LL-3 1 f1 [f1 f2. i 17/1 xjs US. Patent Nov. 25, 1975 Sheet10f33,921,558

Nov. 25, 1975 Sheet2of3 3,921,558

I I Patent Patent Nov. 25, 1975 Sheet30f3 3,921,558

FLOATABLE VESSEL This invention relates to a floatable vessel and ismore particularly, though not exclusively, concerned with such a vesselfor employment as an oil recovery vessel.

In British Pat. Specification No.. 1,106,258 in the name of the presentApplicants, Vickers Limited, there is disclosed a floatable vesselhaving an upright column of relatively small cross-section which carriesa ballast chamber of relatively large cross-section positioned at ornear the lower end of the column, a buoyant superstructure also ofrelatively large cross-sectionw'hich is slidably mounted on the columnfor movement between a lower position adjacent the ballastchamber and anupper position at or near the upper end, of the column, and means forsecuring the superstructure in said upper position. H

Although intended primarily for stationary use, the. vessel is towableto the intended site, and it is to this end that the superstructure isslidably mounted on the column. In this way, the vessel can be towedthrough the water with the ballast chamber relatively unballasted sothat the chamber itself floats in the water, and with the superstructurepositioned adjacent the ballast chamber. In this towing condition, thevessel has a relatively shallow draft as is highly desirable for towingpur-. poses, the draft of the vessel being reduced by virtue of theslidable mounting of the superstructure.

On reaching the site, the ballast chamber can be sunk and thesuperstructure raised to a position at or near the upper end of thecolumn to convert the vessel into its operative condition. The vesselthen has good stability by virtue of its deep draft. a

The present invention aims to employ a vessel essentially of theconstruction referred to, so that it has the advantage of being wellsuited both to towing and operative conditions at sea, and to adapt thevessel for the recovery from the sea of liquid (such as oil), having alower specific gravity than sea water, before the liquid arrives at thesurface of the sea.

According to the invention there is provided a floatable vesselcomprising a single upright buoyantcolumn of relatively smallcross-section whichcarries, at the lower column end, a floatable ballastchamber of relatively large cross-section, a buoyant superstructure alsoof relatively large cross-section slidably mounted on the column, andmeans for securing the superstructure to the column, wherein theimprovement comprises a duct which is defined by the column and ballastchamber and which is open at the lower end of the vessel, and means foradmitting liquid into the duct over a relatively large area.

Then, the vessel may be so positioned that "escaping liquid such as oilwhich tends to rise to the surface of the sea in the form of areasonably coherent column gradually widening out as it ascends may becollected in the means for admitting liquid into the duct.

Preferably, the ballast chamber has a conical base which provides aninverted funnel leading to the duct opening at the lower end of thevessel and constitutes said means for admitting liquid into the duct.With such a construction, the vessel is able adequately to deal withescaping oil under most conditions.

In a preferred construction, the vessel incorporates one or more tanksand means for admitting liquid from the duct into the tank or tanks. Thetank orat least some of the tanks, as the case may be, may then beflooded tobring the vessel into its operating condition. If required,oil from the ascending column of escaping oil may be stored in the tank(where only one tank is present) or in at least some of the tanks,valves located at the top of the ballast chamber being opened and thewater ballast pumped overboard to allow the oil to flow into the spacepreviously occupied by the ballast. It is desirable for the vessel. toincorporate more than one such tank and for these tanks to be housedpartly in the ballast chamber and partly in the column at the lower endthereof. Then, all the tanks may be ballasted in order to submerge thevessel sufficiently to locate the superstructure at the top of thecolumn, the superstructure being secured there. At this point, theballast may be pumped out of each tank in the column to restore thevessel to its operating draft. Ideally, the means for admitting liquidfrom the duct into the tank or tanks comprise pumps.

As mentioned above, escaping oil may be stored in the tank min at leastsome of the tanks as the case may be. However, it is possible for thevessel further to comprise means for pumping liquid in the duct to aposition above the waterline of the vessel. Then, instead of storing theoilas mentioned above, the oil may be pumped directly into an attendanttanker (or Dracone).

The vessel may be provided with venting means comprising an upward ductextension, horizontal trunking to which the duct extension leads andwhich is cantilevered at its outboard end well clear of thesuperstructure, and appropriate gas-tight connections to permit slidingof the superstructure relative to the column whilst maintaining the ductgas-tight. This arrangement is suitable for the purpose of ventingunwanted gas in the duct .to the atmosphere.

In order that the invention may be more fully understood, one embodimentthereof will now be described, by wayof example, with reference to theaccompanying drawings, in which:

FIG. 1 is a diagrammatic elevation of the vessel,

FIGS. 2A and 2B show a fragmentary elevation and a plan view of thecolumn and the ballast chamber of the vessel, and

FIGS. 3A and 3B show similar views of the upper end of the column.

Referring to the drawings in general but FIG. 1 in particular, the.vessel consists of three essential parts, a ballast chamber 1, avertical centre column 2 and a light alloy superstructure 3. The overallheight from the bottom of the ballast chamber to the top of thesuperstructure may, for example, be of the order of 250 feet.

The ballast chamber 1 consists of a cylindrical shell 4 of relativelylarge cross-section and may, for example, be feet in diameter and 32 ft.6 inches in height, and of all-welded mild steel construction employingconventional shipbuilding practice. The cylinder defines a duct section5 which is open to the sea and the bottom of the ballast chamber isformed by a watertight cone 4a providing an inverted funnel leading tothe duct opening at the lower end of the vessel. The interior of theballast chamberis divided by radial bulkheads into eight separate radialtanks 6 arranged around the centre duct section 5 although,alternatively, only a single tank or a number of tanks other than eightmay be accommodated in the vessel.

The column 2 is attached to, and extends upwards from, the ballastchamber and it consists of two sections of different diameters, thelower, larger, section 7 3 extending upwards as far as the operatingwater line, above which a tapered section 8 connects it to the upper,smaller, section 9. The column is also of all-welded mild steelconstruction, ring-stiffened in a manner similar to that of a submarinepressure hull.

The column 2 is divided into a number of watertight compartments 11 bymeans of equally spaced horizontal bulkheads and defines a duct section12 which extends at its upper end to the upper column section 9 andwhich opens at its lower end into the duct section so that the two ductsections constitute a single duct. A lift trunk 13 is disposed in theduct section 12 and extends between the upper end of the column 2 andthe duct section 5. Immediately above the ballast chamber, the lowestwatertight compartment of the centre column comprises a water ballasttank 14 for use during the operation of ballasting the vessel down toits deepest draught to locate the superstructure at the top of thecolumn as will be described and ballast pumps 15 for pumping liquid fromthe duct into the tanks 6 occupy the compartment above.

The watertight compartment at the top of the section 7 houses cargopumps 16, which are required to transfer recovered oil from the duct toan attendant tanker or. Dracone. Around the tapered column section 8, anon-watertight extension 17 of the lower column is provided to protectmanifolding to which transfer hoses are attached and, at the same time,provide a supporting structure for a sliding collar 18 which surroundsthe upper column section 9 for a purpose to be described.

The superstructure 3, which is of relatively large cross-section, isconstructed of aluminium alloy and is slidable on the column between theposition shown in full line in FIG. 1 and a position against the ballastchamber as shown in broken line. In the upper operating condition, thesuperstructure is attached to the column 2 by means of the collar 18,which is also of aluminium. The collar is in the form of an annuluswhich accomodates the difference in diameters of the lower and uppercolumn sections 7 and 9 traversed by the superstructure. Suitableprecautions will be taken to obviate the possibility of galvanic actionoccurring at the bimetallic connection between the aluminium collar andthe steel centre column.

There are three decks in the superstructure, being an upper, helicopter,flight deck, an intermediate deck having a deckhouse enclosing livingaccommodation and a lower deck reserved for machinery and workshops. Thebase of the superstructure is of double walled construction to formcontainers for storing fuel and water. At the upper end of the column,three flats or decks are located to coincide with the three decks of thesuperstructure when the latter is situated at the top of the column.

The above described vessel is convertable between a transit or towingcondition in which the ballast chamber is unballasted and thesuperstructure positioned against the ballast chamber as indicated inbroken line in FIG. 1, when the draft of the vessel will be as indicatedat 19, and an operating condition in which the ballast chamber issubmerged and the superstructure raised clear of the water surface whenthe draft of the vessel will be as indicated at 21, which in theconstruction indicated is I80 ft., leaving the aforementioned cargotransfer hoses 20 ft. above the water line. Means are provided forsecuring the superstructure in either of the positions shown. In thetransit condition, stability is derived from the waterplane inertia ofthe relatively large cross-section ballast chamber and in the operat-'ing condition stability is derived from a positive separation of thecentres of gravity and buoyancy of the vessel, i.e. submarine stability.The procedure to convert from the transit to the operating condition isto admit water into the ballast tanks 6 usually in opposing pairs inorder to maintain the vessel at the correct attitude, with thesuperstructure securing means released. Each tank 6 is provided with asea water valve for this purpose. Thereby, the ballast chamber is sunkand the column drawn down through the superstructure which is floatinguntil the superstructure reaches its upper position at which it issecured.

During the superstructure elevating process all eight radial tanks willbe filled and in order to submerge the vessel sufficiently to locate thesuperstructure at the top of the column, additional ballast will beintroduced to the tank 14. This will then be expelled to restore thevessel to its operating draught. The vessels draught, trim and heel maybe constantly maintained by appropriate adjustments to the remainingwater ballast.

In use, when an oil spill is to be dealt with, for example from adamaged well head installation, a faulty bore-hole or a leaking pipe orfitting on the sea floor, the vessel will be towed, in the towingcondition, to the area of operations and positioned, as far as can beascertained, over the centre of the source of the oil spill. The vesselwill then be converted to its operating condition as described above.

The sea water in the centre column is then evacuated by extraction bythe pump 16 from the upper end of the centre column and dischargedoverboard. While this is being done, the escaping oil will replace thedisplaced water in the base cone 4a and pumping operations will continueuntil all the sea water has been expelled. At this point, pumping willcease and hoses connected to a tanker (or Dracone) alongside, afterwhich pumping can recommence to extract the recovered oil. If it isdesired to store more oil in the vessel, valves located at the top ofthe ballast chamber are opened and the water ballast pumped overboard,allowing the oil to flow into the space previously occupied by ballast.This operation may be performed selectively and compensating wateradmitted to the centre ballast tank 14 as required to maintain draught.The total oil capacity of a vessel of the dimensions specified abovewould be apv proximately 6,000 tons.

Preferably and as shown in FIGS. 1 and 3A, the central duct section 12has an upward extension to the top of the upper column section 9 for thepurpose of venting unwanted gas in the duct to the atmosphere. Theupward extension comprises a suitable central gas duct 22 surroundingthe upper section of the lift trunk 13 and connecting with horizontaltrunking 23 which is below the helicopter deck 18 and cantileveredoverboard and upwards at its outboard end to a point well clear of thesuperstructure as indicated at 24. The trunking will require gas-tightconnections where it passes through the collar 18 and will incorporateflame arrestors as required. The gas tight connections permit sliding ofthe superstructure 3 relative to the column 2 whilst maintaining thecentral duct gas-tight.

In deep water, and it should be mentioned that a vessel of the abovedimensions is capable of dealing with an oil leak from the sea floor indepths down to 250 ft., the escaping oil is likely to rise to thesurface in the form of a reasonably coherent column gradually wideningout as it ascends, in a similar manner to the formation of smoke plumesin air. (The specific gravity of North Sea oil may be as low as 0.81 Thedegree of turbulence transmitted to the column of oil will obviouslydepend on the prevailing current and eddy conditions. However, even inmoderately adverse locations it is clearly an advantage to intercept theoil before it reaches the surface than to collect it afterwards when ithas commenced to spread horizontally over the surface.

I claim:

1. A floatable vessel comprising:

A. an upright buoyant column of relatively small cross-section;

B. a floatable ballast chamber of relatively large cross-section securedto the lower end of said column, said ballast chamber having asubstantially vertical outer peripheral wall, a central portion, and abase, said base defining below substantially the entire ballast chambermeans in communication with said central portion for admitting liquidinto a duct over substantially the entire base area of the vessel;

C. a buoyant superstructure of relatively large crosssection slidablymounted on said column;

D. means for securing said superstructure to said column;

E. a duct positioned within said column having one end thereof extendingover said vessel and the other end in communication with said centralportion of said ballast chamber;

F. liquid storage means in said ballast chamber; and

G. means for admitting liquid from said duct into said liquid storagemeans.

2. A vessel set forth in. claim 1, wherein said base of said ballastchamber is conical and which in combination with said central portiondefines an inverted funnel leading to the duct opening at the lower endof the vessel to comprise said means for admitting liquid into the duct.

3. A vessel as set forth in claim 2 wherein said liquid storage meanscomprises more than one liquid storage tank and ballast tank positionedat the lower end of said buoyant column.

4. A vessel as set forth in claim 2 including means for pumping liquidinto said duct to a position above the waterline of said vessel.

5. A vessel as set forth in claim 1 wherein said liquid storage meanscomprises more than one liquid storage tank and ballast tank positionedat the lower end of said buoyant column.

6. A vessel as set forth in claim 1 including means for pumping liquidinto said duct to a position above the waterline of said vessel.

7. A vessel as set forth in claim 1, including means for ventingunwanted gas in said duct to the atmosphere, said venting meanscomprising an upward duct extension, horizontal trunking in sectionscarried by the super-structure and cantilevered at its outboard end wellclear of said superstructure; and releasable connections for connectingin a gas-tight manner the trunking sections together and to the ductextension when the superstructure is secured in its upper most positionto said buoyant column, said connections permitting sliding of thesuperstructure relative to the column.

8. A vessel as set forth in claim 7 wherein said ballast I chamber has aconical base which in combination with said central portion defines aninverted funnel leading to the duct opening at the lower end of saidbuoyant column to comprise said means for admitting liquid into theduct.

9. A vessel as set forth in claim 8 wherein said liquid storage meanscomprises more than one liquid storage tank and ballast tank positionedat the lower end of said buoyant column.

10. A vessel as set forth in claim 7 including means for pumping liquidinto said duct to a position above

1. A floatable vessel comprising: A. an upright buoyant column ofrelatively small cross-section; B. a floatable ballast chamber ofrelatively large cross-section secured to the lower end of said column,said ballast chamber having a substantially vertical outer peripheralwall, a central portion, and a base, said base defining belowsubstantially the entire ballast chamber means in communication withsaid central portion for admitting liquid into a duct over substantiallythe entire base area of the vessel; C. a buoyant superstructure ofrelatively large cross-section slidably mounted on said column; D. meansfor securing said superstructure to said column; E. a duct positionedwithin said column having one end thereof extending over said vessel andthe other end in communication with said central portion of said ballastchamber; F. liquid storage means in said ballast chamber; and G. meansfor admitting liquid from said duct into said liquid storage means.
 2. Avessel set forth in claim 1, wherein said base of said ballast chamberis conical and which in combination with said central portion defines aninverted funnel leading to the duct opening at the lower end of thevessel to comprise said means for admitting liquid into the duct.
 3. Avessel as set forth in claim 2 wherein said liquid storage meanscomprises more than one liquid storage tank and ballast tank positionedat the lower end of said buoyant column.
 4. A vessel as set forth inclaim 2 including means for pumping liquid into said duct to a positionabove the waterline of said vessel.
 5. A vessel as set forth in claim 1wherein said liquid storage means comprises more than one liquid storagetank and ballast tank positioned at the lower end of said buoyantcolumn.
 6. A vessel as set forth in claim 1 including means for pumpingliquid into said duct to a position above the waterline of said vessel.7. A vessel as set forth in claim 1, including means for ventingunwanted gas in said duct to the atmosphere, said venting meanscomprising an upward duct extension, horizontal trunking in sectionscarried by the super-structure and cantilevered at its outboard end wellclear of said superstructure; and releasable connections for connectingin a gas-tight manner the trunking sections together and to the ductextension when the superstructure is secured in its upper most positionto said buoyant column, said connections permitting sliding of thesuperstructure relative to the column.
 8. A vessel as set forth in claim7 wherein said ballast chamber has a conical base which in combinationwith said central portion defines an inverted funnel leading to the ductopening at the lower end of said buoyant column to comprise said meansfor admitting liquid into the duct.
 9. A vessel as set forth in claim 8wherein said liquid storage means comprises more than one liquid storagetank and ballast tank positioned at the lower end of said buoyantcolumn.
 10. A vessel as set forth in claim 7 including means for pumpingliquid into said duct to a position above the waterline of said vessel.